The goal of the proposed study is to determine if psychosocial manipulations influence the progression to disease and death in rhesus macaques who have been inoculated with SIV, the simian immunodeficiency virus. SIV infection in rhesus monkeys produce a disease considered by many (e.g. IOM) to be the best animal model of HIV infection in humans. One important parallel between SIV infection and HIV infection in their respective hosts is the variable time course to progression to clinical disease and death. Considerable research conducted with humans has implicated psychosocial factors in overall health as well as in progress of diseases such as certain cancers and coronary disease. More recently, alterations in immune system functioning have been reported for macaques who have undergone psychosocial manipulations. To determine whether such psychosocial factors affect disease progression in SIV-infected monkeys, an archival methodology will be employed, using colony records at the three NIH-sponsored Regional Primate Research Centers where simian AIDS research with rhesus macaques is being conducted. After careful screening of potential subjects' records for inclusion in this analysis, records pertaining to rearing history, caging history, medical history, SIV inoculation, and clinical outcome will be extracted for all animals (estimated n=300) and the data analyzed using multivariate techniques. The general hypothesis is that changes in housing occurring both before and after viral inoculation will be related to the latency to onset of various physical and immunological signs of disease. Of particular interest are individual differences in the frequencies of housing changes which involve a) separations from familiar companions, b) introduction to unfamiliar companions, and c) social isolation. Support for the hypotheses would provide the basis for further developing this animal model for use in prospective investigations of the mechanisms by which psychosocial processes affect SIV disease progression. Moreover, results of the proposed study will be valuable not only in directing which social processes are related to slower disease progression, but may have potentially important implications for the delivery of psychosocial services to HIV-infected humans to delay disease onset and enhance physical well-being.